Method and apparatus for



Sept. 16, 1947. M. 5. WHITE METHOD AND APPARATUS FOR CONDUCTING 'ELECTROOARDIOGRAPHIC EXAMINATIONS Original Filed May 22, 1942 4 sheets-sheet 1 E LEOTROOARDIOBRAPH T0 ELECTROOARDIOGRAPH INVENTOR MAJOR 5. WHITE ATTOHNEKJ' Sept. 16, 1947. s w rr r Re. 22,916 METHOD AND AP PARATUS FOR CONDUCTING ELECTROCARDIOGRAP HIC EXAMINATIONS driginal Filed May 22, 1942 4 Sheets-Sheet 2 INVENT'OR MAJOR '8. WHITE M; .M

A'ITOR NEYS Sept. 16, 1947. 5, WHITE Re. 22,916

METHOD AND APPARATUS FOR CONDUCTING ELECTROCARDIOGRAPHIC EXAMINATIONS Original Filed May 22, 1942 4 Sheets-Sheet 5 INVENTOR MIJDR 5. WHITE ATTORN E Y6 M. 5. WHITE Sept. 16, 1947.

METHOD min APPARATUS FOR CONDUCTING ELECTROCARDIOGRAPHIC EXAMINATIONS 4 Sheets-Sheet 4 Original Filed May 22, 1942 :OPQUJUM uoozhuuJu .rzuzkm 20x.

ME NH M 5 RI w w y A-rrcmv EYS Reissued Sept. 16, 1947 METHOD AND APPARATUS FOR CONDUCT- ING ELECTROCARDIOGRAPHIC EXAMI- NATIONS Major Samuel White, Arlington, Va.

Original No. 2,400,583, dated May 21, 1946, Serial hlo. 444,080, May 22, 1942. Application for reissue April 18, 1947, Serial No. 742,403.

(Original granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 12 Claims.

governmental purposes, without the payment to me of any royalty thereon.

This invention relates generally to electrocardiographs but more particularly to a method and means for controlling the path of current through electrodes contacting various parts of the body or bodies of one or more patients under examination to determine heart voltages with respect to different current paths.

Heretofore in making heart examinations it has been common practice to attach one electrode to each of the three limbs of the body of a person during examination and to selectively determine the voltages existing between these points. It has been found desirable in the diagnosis for certain diseases to provide an additional electrical reference point with respect to which the potential at other points and through various paths (including the arms and legs) may be deter-mined. It has been known heretofore from clinical experiments that one such desirable reference point may be obtained by simultaneously placing electrodes on three limbs of the patient and connecting each of these electrodes through a high resistance to a common point. Using this common point as an electrical reference point, the voltage between this point and any other points on the body may be readily determined.

In the prior devices electrical switch means have been provided for pairing the electrodes from the different limbs for determining the potential difference existing therebetween but with these prior devices it is impossible to obtain the reference point, known as the Wilson potential, and to determine the voltage between this point and the other points on the body without removing the connecting wires to the different electrodes.

In the past when it was desired to obtain the potential over the precordium it was necessary to remove one of the limb electrodes and use it as an exploratory electrode in combination with any other reference point on the body. This destroyed the possibility of obtaining the Wilson zero point, or other reference points without requiring considerable time and inconvenience in changing the electrodes or connections to the electrodes.

In accordance with the present invention, means are provided for fixing and keeping an electrode in contact with each of three of the limbs of a person throughout the period of treat- 2 ment, providing an electrical connection to each of said electrodes to establish an electrical reference point corresponding to each electrode and selectively connecting each of these electrodes in such a manner as to provide a fifth electrical reference point and means for measuring the potential difference between all of the combinations of pairs of these electrical reference points without disturbing the limb electrodes. This is a very important feature since it facilitates the obtaming of several combinations of readings in a minimum of time before the conditions under which the tests are being made have changed. For instance, when making such heart examinations it is well known that examinations are taken when the person is first in the rested and relaxed condition and then after the patient has been instructed to perform certain physical exercises in order to stimulate the action of the heart, or vice versa. It is essential that all of the tests be completed before the rate of the action of the heart has appreciably diminished. By the use of the present invention investigations of the heart under these conditions is greatly facilitated.

One object of the invention is to provide a device, used in conjunction with an electrocardiograph by which various current paths from the patient to the electrocardiograph may be selected without the necessity of changing the location of the electrodes on the body of the patient to thus facilitate speed and ease of examination.

Another object of the invention is to provide for use, with the electrocardiograph, of precordial electrodes in addition to the electrodes now commonly used, and toadapt the instrument for the instantaneous selection of current paths from any of the electrodes connected to one or more patients.

With these and other objects in View, the invention consists in a novel method of cardiographic examination of patients, and novel details of construction, combination and arrangement of parts of the apparatus devised to effect the examination, as will be more fully hereinafter set forth and pointed out in the claims.

Referring to the figures in which like parts are indicated by similar reference characters:

Fig. 1 is a perspective exterior view of the housing enclosing the circuit control device for a single patient showing the selector dial and leads to an electrocardiograph;

Fig. 2 is a perspective view of the housing shown in Fig. 1, with top removed, showing the interior 3 thereof with circuit control mechanism and lead connectors;

Fig. 3 is a diagrammatic view of the circuit control mechanism shown in Figs. 1 and 2;

Fig. 4 is-a horizontal section taken on the line 4-4 of Fig. 2, looking in the direction of the arrows;

Fig. 5 is a horizontal section taken on the line 5-5 of Fig. 2, looking in the direction of the arrows;

Fig. 6 is a vertical section taken on the line 5-5 of Fig. 4

Fig. 7 is a detail vertical section taken on the line |1 of Fig. 4; i

Fig. 8 is a perspective view of a modified form of the device showing the exterior of the housing enclosing the circuit control apparatus adapted to form circuits to an electrocardiograph through various pairs of electrodes connected to a group of patients;

Fig. 9 is a perspective view of the housing shown in Fig. 8 with the top removed showing the interior thereof with circuit control mechanism and lead connectors;

Fig. 10 is a diagrammatic view of the multiple patient circuit control mechanism.

Of: the instruments described herein, that shown in Figs. 1 to 7 inclusive is adapted to be used with a single patient and was devised to obtain precordial leads by the various recommended methods as well as the standard leads, so as to obviate the changing of lead wires or electrodes during the process.

The modified form of instrument shown in Figs; 8 to 10 inclusive was designed so that, by operating a switch, it would be possible to connect several patients in succession to a single electrocardiograph machine at a rapid rate, as may be required in certain investigations, or in the examination of large groups.

Referring to the single patient instrument, the wiring diagram Fig. 3 shows the arrangement for obtaining the three standard leads, I, II, III and lead IV of the precordial or exploring electrode. By the simple additional connections as shown diagrammatically in Fig. 3, the device can be arranged so that one-st'ep movements of the switch will successively pair, electrically, the precordial or exploratory lead (through means of the various switch contacts) with the leads which are connected respectively to the left arm, right arm and the left leg. The different switch positions connect the difierent electrodes fixed to the body, as

- well as the exploratory electrode which is adapted to be placed at different points on the body during examination, so that the values of the current and voltage developed in the body due to heart action may be determined by an electrocardiograph between the following points: position I, left arm and right arm; position II, left leg and right arm; position III, left leg and left arm; and position IVT, the exploratory electrode which may be placed at any point on the body, including the precordium or chest and the so-called zero potential'of Wilson.

The operation of an electrocardiograph is based upon the fact that the action of the heart in the human body is accompanied by small volt ageimpulses of the order of .001 volt between the arms or legs. When taking electrocardiograph readings between any two points on the human body there are simultaneously present a plurality of electrical currents or potentials of different polarities and values. However, there is usually a resultant predominating electrical current and potential which gives an indication of the heart axis. In order to reduce as far as possible the effect of the disturbing potentials it has been found that a valuable electrical reference point may be obtained by connecting each of the arms and one of the legs, usually the left, through suitable non-inductive resistances to a common point. By this arrangement the resultant electrical current and potentials are substantially zero at this point. This is commonly referred to in the medical profession as the zero potential of Wilson although, of course, it will be readily understood that this is merely an electrical reference point and is obtained by connecting leads or conductors from the left and right arms and the left leg of the patient each through a 5,000 ohm non-inductive resistance. At this central point or terminal, the potential is so near zero throughout the heart cycle that it may be so considered without encountering serious error. When the switch is moved to position IV'I, as shown in Figure 3, the exploratory electrode is electrically paired with this central terminal electrical reference point, or zero potential of Wilson; at position IVF with the electrode on the left leg; at position IVR. with the electrode on the right arm; and at position IVL with the electrode on the left arm. It will be readily understood that when the switch is in such a position that arm (Figure 3) connects one'of the terminals of the electrocardiograph to the exploratory electrode (positions IVT, IVF, IVR and IVL) the exploratory electrode may be placed at any point on the body including the precordium or chest position so that the potential at any point on the body may be measured, selectively, with respect to the points on the body in contact with the electrodes on the left arm, right arm, left leg and the so-called zero potential of Wilson. By referring to Figure 3 it will be seen that when the arm of the switch 85 rests on the contact 8| the switch arm 88 will rest on contact H, the switch arm 81 will rest on contact 65 and the switch arm 88 will rest on contact 85 thereby establishing the electrically neutral reference point herein referred to as the zero potential of Wilson and will connect this neutral electrical reference point to the conductor 58 which is adapted to be connected to one terminal of the electrocardiograph. As shown, switch arm 85 is connected to conductor 31 which is adapted to be connected to the other terminal of the electrocardiograph. I

The term leads appearing herein is used in the sense to which it is normally referred in the medical profession to indicate the electrodes which are placed in contact with the different points on the body together with their associated electrical conductors. For a definition of the zero potential of Wilson reference is made to Clinical aspects of the electrocardiogram, by Harold E. P. Pardee, M. D., fourth edition, revised, published by Paul B. Hoeber, Medical Book Dept, Harper & Bros. Inc., page 327.

The term precordium or exploratory electrode is used ordinarily in the medical profession to designate the fourth electrode described herein which is not adapted to be fixed during examination to a point on the body of the patient. It is sometimes referred to solely as the precordial lead because the precordium is one of the main points or positions on the body with respect to which it is desired to measure the electrical voltage on one of the limbs, although during examination it isusually moved to various points on the body and its use is not at all limited to the pre-- cordium position. It is believed that the term exploratory is a much more apt term which defines the use of this lead.

In the multiple patient instrument, four electrodes are attached to the patient; three to the usual extremities and one, a precordial or exploring electrode, to the precordium. Each electrode may be connected to a four-prong polarized plug by a four conductor cable or to regular p1ugin connectors as shown in Fig. 10. Any number of patients (in this case four) may be so connected. Each plug is inserted into a polarized plug-in connector or jack on the left-hand side of the switch box. This switch box has two control switches. The first (A) (Figs. 9 and 10) selects the patient whose record is to be taken at the moment. The second switch (B) (Figs. 9 and 10) selects any one of the four leads which it is desired to record from the electrodes connected to a patient. On the right hand end of the switch box is a polarized jack or plug-in connection in which is inserted a plug connected to two wires leading directly to the electrocardiograph. Any two lead wires of the electrocardiograph may be connected to the plug with due regard to polarity. The corresponding lead is then selected by the lead switch on the control panel of the electrocardiograph.

With the switches used in the instrument, there are a sufiicient number of contact points so as to make it possibl to add more patients if so desired, or additional combinations of leads.

Referring to Fig. 1, the numeral it indicates an electrocardiograph provided with leads l I and I2 which are connected to the terminals 53 and I4 of a selector l5 shown in Figs. 2, 6 and '7.

The selector I 5 which is mounted within a housing I6 is of the rotary type and is constructed with a disc shaped index base I! having laterally projecting ears l1, and a plurality of switch bases or plates l8, I9, 2i] and 2! formed of insulating material and provided with laterally projecting ears l8, I9, 20' and 2 l drilled to receive bolts 22.

The index base i! and the switch bases l8, I9, 20 and 2| mounted upon the bolts 22 are spaced from each other by sleeves 23.

The index base is provided centrally with a collar 24 having a flange 25 adapted to form a seat and a threaded portion which is adapted to be fitted into an opening in the front wall of the housing 16 and retained therein by means of a nut 25. The index base I! is provided with circumferentially spaced raised portions 21 over which rollers 28, attached to the opposite sides of an index arm 23, pass, as will be further described.

Within the sleeve member 24 which is attached to the index plate I1 is rotatably mounted an indicator shaft 30 to which is rigidly connected a turning knob 3| provided with a pointer 32 which is adapted to move over a dial 33 attached to the housing It]. The end of the shaft 3%) is squared to fit a central opening in a turning disc 34.

The turning disc 34 is provided with a curve projection 35 which fits into an Opening 36 in the index arm 29 so that with rotation of the indicator shaft 39 the index arm which is formed of spring metal is revolved so that the rollers pass over the raised portions of the index plate to indicate a number of contact points marked on the dial 33. The indicator shaft 30 is slotted to provide for the attachment of a non-circular conductor 6| to branch leads [4 and T5.

6 shaft 3! which projects through centrally located circular openings 38 in the switch bases.

In addition to the large central opening 33, the switch bases [8, I9, 20 and 2| are each provided with a circumferentially arranged row of rectangular openings 39. Within these rectangular openings 39 are fitted a plurality of spring fingers or contact members which are generally designated by the reference character 40. These fingers are crimped so that a portion of them may, due to their elasticity, clamp themselves within the openings, as shown in Fig. 6. In the discussicn relative to the operation of the device hereinafter to be given, the fingers 46 will each be given individual reference characters. These spring fingers are each provided with semi-spherically formed ends ll which are adapted to electrically contact bridging members 42 which are inserted within openings in rotatable discs 43 mounted on the central non-circular shaft3l.

The rotatable discs 43 are circular, formed of insulating material, and provided with a central slotted opening 44 adapted to fit the non-circular shaft 3?. Beneath each of these discs 43, and. contacting them, is placed a metallic non-rotatable disc 45, which discs are each provided with a radially extending projection 46 connected to a lead wire 41 or 48.

These metallic discs 45 are rigidly attached to a, lower insulating disc 49 which is supported by brackets 55 which extend from the switch bases and are provided with curved projections which enter openings in the discs 49.

As shown in Fig. '7 the metallic discs 49 are retained in position by the brackets 55], and projec- I tions :idwhich are crimped in the same manner as the fingers at so that the crimped portions may inserted into an opening in the: switch bases Is, 20 and 2|. 7

The electrodes 5i, 52, 53 and 54 shown diametrically in Fig. 3, and which are attached to the left arm, right arm, left leg-and to a precordial electrode on a patient, are connected to the patient leads 5!, 52', 53' and 54 which are in turn connected to the plug-in connectors 55, 56, '51 and 518. From these connectors, selector leads 59, 60, El and 52 pass to spring fingers or contacts generally termed it on the switch bases.

The connector 55 is connected through the conductor 59 to the contact 63 on switch plate l8, contact 55 on switch plate l9, and to the contact 65 on switch plate 29 through the resistance 66, and through a branch lead 52? to contact 55 on switch plate IS.

The connector 56 is connected through the conductor 50 to the contacts 6'! and 68 on switch plate l9 and through the branch lead 69 and re- 7 sistance 10 to contact (I on switch plate l9, and through branch lead 12 to contact 13 on switch plate [9.

- The connector 57 is connected through the The branch lead It is connected to contacts 16 and ii on switch plate 13 and to contact 18 on switch plate It. The branch lead 15 is connected through resistance 79 to contact 8i] on switch plate 2!.

The connector 58 is connected through conduct-or E2 to the contacts 8|, 82, 83 and 84 on switch plate I8.

The movable contacts which are mounted in the centrally located insulating discs t3 as shown in Figs. 4 and 6 are adapted to rotate with the non-circular shaft 31 and are indicated by the numerals 85, 85, 81 and 83 in the diagrammatic representation in Fig 3. in fjthi s "figure [the switch blades i 85, -86,f8'1 and BB'frepr'esent f 'the metallic discs'45 and contactsiz'which are" connected to-the-leads-4Iand48as shown in Fig. 2.

'It will be noted that any of patientcircuits, i. e., from the left arm and right armelectrodes, are completed in the following manner: from the left arm through conductors to aspringarm 40 on a switch plate, and from the spring arrn to a contact pin 42, and throughametallic disc45 to the electrocardiograph, and from 'the' electrocardiograph through a disc 4'5, througha'pin 42to another spring -arm40, and through areturn' lead to" the electrode on the right arm of the'patient.

In the multiple patient selector illustrated by Figs. 8, 9 and the construction and'arrangemerit of the plate members is similar to the single patient device.

In this device, 'two'selec'tors are used'both of Which are attached to 'thefront Wall of' a housing as illustrated in Figs.8 and 9. Since the construction and operatio'n'of these selectors arethe same as described above, it will only be necessary to describe'their manner of'sele'cting circuits by reference to the diagrammatic illustration as represented in Fig. 10.

In Fig. 10 the numerals "89, '90,;9I and 92 indicate portions of the side wall of the selector housing 93 in which are mounted four groups of plug connector elements for the reception of plug terminals at the extremities of the-patient leads.

In order to trace the circuits connecting'pairs of electrodes contacting the patients numbered 1, 2, 3 and 4, inclusive, the'electrical connection from the left arm, right arm, left leg and the preco'rdial electrode on each patient will be taken in the numerical order of the patients and traced first to the patient selector.

From patient No. 1: the left'arm'e1ectrode95 is connected by the patient lead '91 to the pl connectorSB, and the plug connector 98 is connected through conductor 99 to th'econtactmember I99 of the left arm group of the patient selector, indicated by the letters L. A.; 'the right arm electrode 'IIlI is connected by lead "I02 to connector I03, and the connector 103 is connected through conductor I04 to the contact member I85 of the right arm group'of the patient selector, indicated by the letters R. A. g the left leg electrode IllB'is connectedby lead Ifllto connector I38, and the connector IE8 is connected through conductor 199 t the contact member I In of the left leg group indicated by the letters L, L.; the precordial electrode III is connected by lead I I2 to connector I13, and the connector II3 is connected through conductor M4 to contact member 5 of the precordial gr'oup of the patient selector, indicated byth'e numeral IV, v

From patient No.2: the left'armelectrode I I3 is connected by the patient lead II! to the plug connector I I 8, and the plug connector 1 I815 connected through conductor II 9 to the contact member I29 of the left'arm group of the patient selector, indicated by the letters -L. A.; the right arm electrode I 2I is connected by lead "I22 to connector I23, and the connector I23 is connected through conductor I24 to the contact member I25 of the right arm group of the patient selector, indicated by the letters R. '41,; the left leg electrode I26 is connected by 1ead'I2'I to connector I28, and the connector I128 is connected through conductor I29 to the contact member I39 of the left leg group indicated by the letters L. L.; the p'recordial electrode I3I is connected by lead I32 to connector "I33, and the connector I 33 is connected through co'nductor"l34 to' colitact member I35 of the precordial group of the patient selector, indicated by thenumeral IV.,

From patient No. 3: the left arm, electrode I36 is connected by the patient lead" I31 to, the p connector I38 and the plug connector I38 is con nected through conductor I33 to the contact member I40 of the left arrn'group of the patient selector, indicated by the letters L.A.; the right ar'm' electrode MI "is connected by lead I42 to connector I43 and the connector I43 is connected through conductor I44 to the contact member I 45 of the right arm group of the patient selector, indicated by'the letters R. A; the left leg electrode I46 is connected by lead I41 to connector I48, and the connector I48 is connected through conductor I49 to the contact member I50 of the left leg group indicated by the letters L. L.; the precordial electrode I5I is connected by leadI'52 to connector I53, and the connector I53 is connected through conductor I'54'to'contact member I55 of the precordial group of the patient selector indicated by the numeral IV.

From patient No. 4: the left arm electrode I53 is connected by the patient lead I5? tothe plug connector I58, and the plug connector 58 is connected through conductor H59 to the contact member H59 of the left arm group of th patient selector, indicated by the letters L. A.;v the right arm electrode 15? is connected byle'ad I62 to connector IE3, and the connector [63 is connected through conductor I 54 to the contact member I 65 of the right arm group ofthe patient'sele'ctor, indicated by the letters R. A.; the left leg electrode IEGis connected by lead It! to connector I68, and the connector I58 is connected through conductor I68 to the contact member I19 of the leftleg group indicated bythe letters L. L.; the precordi'al electrode IEI is connected by lead I12 to connector I13, and the connector I13 is connected through conductor I I4 to contact member II5 of the precordial group oftliepatient selecton-indicated by'the numeral IV.

The contact members of the left arm, right arm left leg, and the precordial groups of the patient selector, are connected electrically to the contacts of theelectrodejgroup as, follows: contact members I89, I23, 'liltl'and I99 of the left arm group L. A. may be connected selectively, through the rotatable contact member Il'fi and leads err d I'll, to the contacts ns and us of the elec'trode selector; contactmembers I 95, I25, I45 and I55 of the right arm group R. A. may be connected selectively through the rotatable contact member I30 and leads I8I and NH to the contacts I32 and I83 of the electrodeselector; contact members H9, I39, I59 and I79 of the left leg group L, L.may be connected selectively through the rotatable contact member I84 and leads I85, I85, and I98 to contacts I86, I81 and I88 of the electrode selector; and contact members I15, I35, 155, and'l15 or th'eprecordial electrode group IV may be connected selectively through the rotatable contact member I89 and the lead I99 to contact Iel of the electrode selector.

Contacts I18, I 88, I81 and I9I of the electrode selector may be connected selectively through the rotatable contact member I92 and leadsI3 to the positiveterminal I94 of the electrocardiograph, and contacts I92, I33, I79 and I88 may be connected through the rotatable contact member I92 and lead I535 to the negative terminal I9"! of the electrocardiograph.

To illustrate the operation of both the single patient and multiple patient apparatus, a circuit through a pair of electrodes to the electrocardio graph in each device will be described and with this description and the description of the entire wiring system as given above, it will be a simple matter to trace an of the circuits used.

If a circuit through position I of the single patient device is chosen, then from the left arm electrode (Fig. 3) the current will pass through lead 5|, plug-in connector 55, conductor 59 to contact 63, and from contact 68 through switch blade 85 (which represents the metallic disc 45 in Fig. 6) to lead 41 of the electrocardiograph, and from lead 48 of the electrocardiograph through switch blade 86 to contact 81 and thence through conductor 68 to plug-in connector 56 to patient lead 52, and to the right arm electrode 52.

When the pointer is moved to position II, the circuit is from the left leg electrode 53 to terminal contact 16 through switch blade 85, through conductor 41 to the electrocardiograph and from the electrocardiograph through conductor 48 to switch blade 89, contact 68, to the right arm electrode 52.

For the third position, or whenthe pointer is moved to III on the dial, the circuit is from left leg electrode to terminal 11 through switch blade 85 through conductor 41 to the electrocardiograph and from the electrocardiograph through conductor 48 to switch blade 86, contact 84 to the left arm electrode 5I.

At position IVT the circuit is from the precordial electrode 54 to contact 8| through switch blade 85 and conductor 41 to the electrocardio graph, and from the'electrocardiograph through conductor 48 and respectively through switch blades 86, 81 and 88, contacts 11, 65 and 89 and resistances 10, 66 and 19 to the right arm, left arm and left leg electrodes 52, 5| and 53,

When the pointer is moved to IVF the circuit is from the precordial electrode 54 to contact 82 through switch blade 85 and conductor 41 to electrocardiograph and from the electrocardiograph through conductor 48, switch blade 41, and contact 18 to the left leg electrode 53.

When the pointer is moved to IVR the circuit is from the precordial electrode 54 to contact 83, through switch blade 85 and conductor 41 to the electrocardiograph and from the electrocardiograph through conductor 48, to contact 13, and through the switch blade 89 to the right arm electrode 52.

The pointer when moved to IVL completes a circuit from the precordial electrode 54 to contact 84, through switch 85 and conductor 41 to the electrocardio-graph, and from the electrocardiograph through conductor 48, switch blade 86 and contact 65', to the left arm electrode 5I.

The multiple device as mentioned above is provided with two selectors, a patient elector, having four positions, one for the selection of each of four patients, and an electrode selector having four positions, one for each of four circuits, namely, I from the left arm and right arm electrodes, II from the left leg and right arm elec trodes, III the left leg and left arm electrodes, and IV the precordial and left leg electrodes.

The circuits for the I, II, III and IV positions of patients No. 1, No. 2, No. 3 and No. 4 are as follows:

Patient No. 1, position I (left arm and, right arm). From left arm electrode 96 to contact I00, switch blade I15, contact I18, switch blade I92, contact I94 to electrocardiograph. From III) electrocardiograph to contact I91, switch blade I92, contact I82, switch blade I8, and contact I05 to right arm electrode I0 I.

Patient No. 1, position II (left leg and right arm). From left leg electrode I06 to contact H0, switch blade I84, contact I86, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I82, switch blade I88, contact I83, contact I95, and to right arm electrode IOI.

Patient No. 1, position III (left leg and left arm). From left leg electrode I06 to contact IIIl, switch blade I84, contact I81, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I19, switch blade I13, contact I00, to left arm electrode 98.

Patient No. 1, position IV (precordial electrode and left leg). From precordial electrode III to contact II5, switch blade I89, contact I9I, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I88, switch blade I84, contact I I0 to left leg electrode I05.

Patient No. 2, position I (left arm and right arm). From left arm electrode I22 to contact I20, switch blade I16, contact I18, switch blade I82, contact I94 to electrocardiograph. From electrocardicgraph to contact I91, switch blade I92, contact I82, switch blade I80, contact I25 to right arm electrode I2 I Patient No. 2, position II (left leg and right arm). From left leg electrode I26 to contact I99, switch blade I84, contact I86, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I83, switch blade I80, contact I25 and right arm electrode I2I.

Patient No. 2, position III (left leg and left arm). From left leg electrode I26 to contact I30, switch blade I81, switch blade I92, contact I94 to electrocardiograph. From the electrocardiograph to contact I91, switch blade I92, contact I19, switch blade I16, contact I28, to left arm electrode H8.

Patient No. 2, position IV (precordial electrode and left leg). From precordial electrode I3I to contact I35, switch arm I89, contact I9I, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I88, switch blade I84, contact I30 to left leg electrode I26.

Patient No. 3, position I (left arm and right arm). From left arm electrode I42 to contact I48, switch blade I16, contact I18, switch blade I92, contact I84 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I82, switch blade I88, contact I45 to right arm electrode I4I.

Patient No. 3, position II (left leg and right arm). From left leg electrode I46 to contact I50,

switch blade I84, contact I86, switch blade I92,

contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I89, switch blade I88, contact I45 to right arm electrode I4I.

Patient No. 3, position III (left leg and left arm). From left leg electrode I46 to contact I59, switch blade I84, contact I81, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I19, switch blade I16, contact I401 to left arm electrode I36.

Patient No. 3, position IV (precordial electrode and left leg). From precordial electrode I5I to contactgl55;;switch;1b1aded 89, contact I9I-, switch blade: I92; contact I945 to: electrocardiograph. From electrocardiographgtozcontact; I91, switch blade I92, contact I88; switch blade I845, contactrl 50 to left legv electrode 146;

Patient No. 4, position- I (leftarnnandqright arml. From left-arm'electrode I56, contact I69, switch-blade I16; contact. I18,. switch blade I92, contact; I 94 to. thezelectrocardiograph From the electrocardiographito contact. I91, Switchblade I92, contact I82; switch blade I80; contact' I95 torright arm electrode I I] I PatientrNio. 4, position II (leftle'gcand right arm). Fromtheleftrleg electrode I66 to. contact I19; switch" blade [84, contact I86; switch blade I92, contact I94 torth'e electrocardiograph. From the electrocardiograph tocontact- I91; switch blade-I92, contact I83, switch' blade- I89; contact I65 to electrode IBI.

Patient No. 4; position III (left leg and left arm) Fromleft' leg electrode I66 to contact I10, switch blade I84, contact I81, switch blade- I92,-

contact I94 to the electrocardiograph; From th'eelectrocardiograph to contact I91; switch blade I92 contact I19, switch-blade I16; contact I43 to-left arm electrode I35:

Patient No. 4, position IV (precordial electrode and-'left leg). From the-preeordial electrode I1I to contact I15, switch bladeI89; contact IQI, switch blade I92, contact194to the-electrocardiograph. From the electrocardiograph to contact I91,- switch I92, contact" I88; Switchblade I84, contact I to left 'leg electrode-I66.-'

Although in theforegoing certain-- elements have been describedas best adapted to perform the-functions=a1lotted to them, neverthelessit is to be understood that-certain changes maybe resorted to without departingfrom the spirit and scopeof the inventionas disclosed in the-appended claims.

Having described my invention; What I claimas new-and desireto secure by Letters Patent'is:

1. In" combinationwith "an electrocardiograph, a-selecting device comprising a patient selector provided with contact members electrical-ly con nected with electrodes attachedto a plurality of patients,-anda contactiselectoradapted ,to-selectively I contact said contact members; and an.

electrodeselector' provided with contact; members connectedelectrically-with saidcontact selector, and an-addi-tional contact-selector connected with the leads ofan-electrocardiograph and adapted to selectivitycontact-the contact members of said-electrode selector; whereby elec trodes attached to any of-the patients may be selectively connected with the leads of the electro: cardiograph.

2. In combination withelectrocardiograph, a, selecting device comprising a patient, selector provided with circularly, arranged contact 'members electrically connected with: electrodes at tached to 'a-plurality of, patients, and adrotatable contact selectoradapted tocontact said contact members; an electrodeselector providedwith cir cularly arranged contact members; connected electrically with said contact selector," ancla rotatable-contactselector connected with the leads ofelectrocardiograph adapted to contact the contact membersof said electrode selector to selectively establish circuits through the electrodes and the-leads of the electrocardiograph- 3. In combination withan electrocardiograph,

selecting devices comprising; a patient-selector including a plurality of'sta-tion-ary contactmembers electrically 'connected to patientelectrodes,

1'2 and -;movable contact ,membersadapted to; selectively' contact any of'said; stationar contactmembers; andan electrode selector including'a plurality; Of stationary contact membersrelectrically connected: to the stationary contact members and the movable contact-members-ofsaid patient-selector, said electrode selectorbeing provided. with movableycontact :m-embers connected electrically with an electrocardiograph and tients, the respective groups serving; to connect simultaneously a'series of patientswith said: com nector: means, a patientselector permanently connectedt'with said connector meansandpperable for selecting one of said patients and the electrode group associated therewith, and switching', means in electrical relation. with thepatient selectorand with the positive and negative electrode terminals of said :electrocardiograph machine for establishing.electrocardiographic leads from'th'e patientand electrode group selectedrby said patient selector, to said. :electrocardiograph machine;

5. In an apparatus of the class described 'for group examination-of a series of patients, the

, combination with an: electrocardiographma:

chine including its positive and negative. elec trodes; of electrode connector means, a, plural-' ity of patient electrodes attached. in groups to said connector means, each electrodegroup including a precordial and a series :ofrlimb electrodes adapted to be operatively associated with one I of said patients, the respective groups serving to connect simultaneously a-ser-iesof patients with said connector means, a patient selector permanently connected with means and operable for selecting one -of said paients and the electrode group associated :therewith, and switching means in electrical relation with the patient selector and with the positive and negative terminals of" saidelectrocardiograph machine for connecting a pair of electrodes in the electrode group selected 'by said patient selector with saidelectrocardiograph machine.

6. In combination with'an electrocardiograph having input terminals, a plurality of at least three electrodes adapted to be kept in contact with different pointson the body of" a person during examination, an additional electrode adapted to be placed at will in contact with dif ferent points of the body for= exploratory purposes, and means electrically interposed between said input terminals and said electrodes selectively to pair, electrically any of said electrodes, and to connect said plurality of electrodes to a common point'and to pair saidadditional electrode with said common point.

'1. In combination with an electrocardiograph having input terminals, a; plurality of electrodes some of which are adapted to be kept in contact with a plurality of spaced points on the body of a person during examination, at least one additional electrode adapted -to be. placed at will on the body of the person as an exploratory elecsaid connector said input terminals trode, and means electrically interposed between said input terminals and said electrodes for alternatively, electrically associatin any two of said plurality of electrodes into an electrical pair and for electrically, associating with said additional electrode any one of said plurality and a point. electrically common to said plurality of electrodes.

8. In combination with an electrocardiograph having input terminals, a plurality of electrodes some of which are adapted to be kept in contact with a plurality of spaced points on the body of a person during examination, at least one additional electrode adapted to be placed temporarily in contact with different points on the body of the person as an exploratory electrode, means electrically interposed between said input terminals and said electrodes for selectively forming an electrical pair including one of said plurality of electrodes and said additional electrode and for electrically associating into an. electrical pair two of said plurality of electrodes, and means including said first named means for electrically connecting said plurality of electrodes with an electrically common point and associating in an electrical pair said common point and said additional electrode.

9. In combination with an electrocardiograph having input terminals, a plurality of electrodes some of which are adapted to be detachably fixed to a plurality of spaced points on the body of a person during examination, at least one additional electrode adapted to be placed temporarily on the body of the patient as an exploratory electrode, non-inductive resistances connected between each of said electrodes and a common point, and means electrically interposed between and said electrodes for selectively forming an electrical pair including said additional electrode and said point, and for electrically associating into an electrical pair any two of said plurality of electrodes or any one of said plurality of electrodes and said additional electrode.

10. In an apparatus of the type described, the combination of an electrocardiograph having input terminals, a plurality of at least three electrodes adapted to be in contact with the body of a person during examination, an additional electrode adapted to be placed at will in contact with different points of the body for exploratory purposes, contacts connected to each of said electrodes to constitute an electrical reference point corresponding to each electrode, and switch means for connecting said contacts to establish a fifth electrical reference point and for selectively connecting any combination of pairs of said electrical reference point to said input terminals.

11. In an apparatus of the type described, the combination of an electrocardiograph having input terminals, a plurality of at least three electrodes adapted to be in contact with three limbs of a person during examination, an additional electrode adapted to be placed at will in contact with different points of the body for exploratory purposes, switch means between said input terminals and said electrodes comprising a plurality of contacts each of which is connected with one of said plurality of electrodes, and an additional contact connected to said additional electrode, and movable contact members for alternatively connecting to said input terminals any two of said plurality of contacts or any one of said plurality of contacts and the contact for said additional electrode and to simultaneously connect all of said plurality of contacts with one of said input terminals and the contact for said additional electrode to the other of said input terminals.

12. A system for selectively putting into an electrocardiograph, electrically, voltage values derived from electrodes placed in skin contact with different parts of the body, said system including a group of at least three electrodes adapted to be connected through resistances to provide a neutral point; and an additional exploratory electrode to be placed at will at various points on the body; and a switch having contacts electrically connected, respectively, to the electrodes for establishing said neutral point, said exploratory electrode and said electrodes of said group, at points which exclude said resistances; said switch being interposed between said electrocardiograph and said electrodes and including means for selectively associating the following in electrical pairs: the contact electrically related to said neutral point and said exploratory electrode, the contacts connected directly to any electrode of said group with the contact electrically related to said exploratory electrode, and the contacts electrically connected directly to the electrodes of said group, one with another.

MAJOR SAMUEL WHITE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

